National survey of dietary supplement resources at drug information centers.
D003625:Data Collection; D016208:Databases, Factual / Q000706:statistics & numerical data; D019587:Dietary Supplements / Q000706:statistics & numerical data; D004346:Drug Information Services / Q000706:statistics & numerical data*; D020407:Internet / Q000706:statistics & numerical data; D012014:Reference Books, Medical; D014481:United States